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Translation of abstract (English)

The present work deals with the production of pellets by extrusion and spheronisation. The effects of formulation and process parameters and their influence on pellets characteristics were investigated. The aim of these investigations was to obtain formula to predict the pellet properties in advance. The yield of a pellet batch was found to be dependent on the amount of added water. For binary mixtures of a model drug and microcrystalline cellulose (MCC), a linear relationship between the optimum water content and the fraction of MCC was found. With the aid of substance-specific constants the optimum water content of a mixture could be calculated. The pellet diameter depends on the formulation as well. The main influence results from the fraction of MCC in the mixture and the related water content. Three mathematical models for the prediction of the pellet diameter were compared. The model showing the best correspondence was based on the experimental determination of substance-specific factors. The roundness of pellets was influenced by the amount of added water. At an optimum water content (defined by the yield of pellets), the roundness was always in an optimum range, too. No clear dependency could be found for the bulk density of the pellets and values for the pellets� tensile strength showed a wide variation, which made it difficult to evaluate the results. Nevertheless, a formula to predict the tensile strength could be set up and works well with regard to the accuracy of the measurements. Drug release rate from these matrix formulations was mainly influenced by physical characteristics of the drug. For the three model drugs used in this work, three different groups of drug release properties could be defined. By classifying a substance to one of these groups, the drug release behavior could be predicted. Several combinations of equipment were used to produce pellets in this work. The comparison of these methods showed that pellets can be obtained with all investigated combinations, but each method had different requirements on the formulation, and pellets showed some differences in their properties. These differences can be compensated by using method-specific factors, for example for optimum water content, diameter and tensile strength. The Spheronisation step was investigated separately from the complete process to determine the optimum process conditions. Two drying methods for the pellets were also compared regarding their interchangeability in the manufacturing process. It could be shown that tray- and fluidized-bed drying led to the same results.